Commercial manufacture of nonfugitive polyurethane amine catalysts, i.e., hydroxy-containing amine catalysts, is becoming more important as environmental regulations become more stringent. A common design approach to nonfugitive catalysts is to prepare hydroxyl-containing analogs of existing tertiary amine catalysts. For example, diethylenetriamine (DETA) is reductively alkylated with formaldehyde to give N,N,N',N',N"-pentamethyldiethylenetriamine (PMDETA), a commercial tertiary amine blowing catalyst. A nonfugitive analog of PMDETA is N-2-hydroxypropyl-N,N',N',N"-tetramethyldiethylenetriamine (HPTMDETA) prepared by first reacting propylene oxide with DETA (Equation 1), followed by reductive alkylation with formaldehyde (Equation 2). ##STR1##
The principal hurdle to overcome in this HPTMDETA process is the fact that large excesses (100-200%) of DETA must be employed to achieve high (80-90%) yields of monopropoxylated product. The excess unreacted DETA may, of course, be recycled, but this requires an intermediate distillation and, as such, precludes conducting the two reactions in a simplified one-pot process.